How do I parent the head and the tail of a bone to two different meshes/empties?
Here is a possible way using bones "stretching", in pose mode,  to their top/bottom empties (trackers), not sure you want this, but, anyway here is how it works:



I've set an armature copy location to the bottom tracker, so the head of the bottom bone follows it. But the pose mode contraint stretches to the top tracker, too.